Evaluation of solution culture techniques for studying aluminium toxicity in plants

Abstract

The complexity of acid soils makes it difficult to study the mechanisms of plant tolerance to aluminium (Al) toxicity with soil-grown plants. These problems may be avoided to a large extent by using solution culture. However, reported solution Al concentrations tolerated by the same species often differ by more than one order of magnitude. Possible reasons for such differences include: (i) solution composition effects on the precipitation, polymerization, and activity of Al; (ii) the ameliorative effects of specific ions on plant sensitivity to soluble Al; and (iii) the effects of specific ions and ionic strength on root morphology and physiology. Lotus pedunculatus cv. Grasslands Maku (Al-tolerant) and L. corniculatus cv. Maitland (Al-sensitive) were grown in nutrient solutions with low (2300 μM) and high (22000 μM) ionic strength. Four Al treatments were imposed with monomeric Al activities Almono of 0 to 21 μM. In solutions of low ionic strength, the yield of Grasslands Maku was not affected by Al, but that of Maitland was decreased by ⩾40% with ⩾8 μM Al mono. In contrast, the growth of neither cultivar was decreased with 21 μM {Al mono in solutions} of high ionic strength. The results show the importance of conducting studies on Al toxicity in test solutions that approximate the soil solution’s composition, ionic strength and Al activity.